p2pwnc wireless community network cmsc 711: computer networks yee lin tan adam phillippy
Post on 19-Dec-2015
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TRANSCRIPT
Introduction
♦ Ubiquitous Internet access is a necessity♦ Email, web, VoIP, messaging, remote
network access♦ Current state♦ Internet access far from ubiquitous♦ Required infrastructure not yet in place
♦ Wireless Internet Service Providers (WISPs)♦ Coverage limited to selected hotspots
♦ Wireless LAN (WLAN)♦ Deployed in homes, schools, airports, etc.
♦ Idea♦ Why not unite all WLANs to provide
ubiquitous access to the Internet?
Peer-to-Peer Wireless Network Confederation (P2PWNC)
♦ Framework for uniting WLAN hotspots
♦ Community of administrative domains that offer wireless internet access to each other’s users
♦ P2P network of domain agents (DA)
Peer-to-Peer Wireless Network Confederation (P2PWNC)
♦ Administrative Domain♦ Examples:
♦ Residential hotspot with 1 access point♦ WISP with access points in many locations
♦ Domain Agent (DA)♦ Each administrative domain maintains 1 DA♦ Physical node that represents the WLAN♦ Responsibilities:
♦ Regulates wireless service provision and consumption
♦ Eliminates need for roaming agreements
Peer-to-Peer Wireless Network Confederation (P2PWNC)
♦ Simple accounting mechanism based on token-exchange♦ When roaming in another P2PWNC
domain♦ To compensate for resources
consumed, home DA transfers tokens to visited DA
P2PWNC Design
♦ Based on reciprocity♦ Domains must provide resources
to visitors ♦ So that their own users can
consume resources of other P2PWNC domains when roaming
Distinctive Characteristics
♦ Open to all♦ No registration or central authority
♦ Joining P2PWNC is similar to joining a file-sharing network
♦ Free to use♦ No barrier to entry♦ Reciprocity drives the system
♦ Autonomous domains♦ Each domain decides how much resources
it wants to provide to visitors♦ Protects privacy♦ Identity and location privacy
P2P Systems
♦ Communities of economic agents cooperating for mutual benefit without centralized control
♦ Characteristics:♦ Makes use of otherwise underused
resources♦ Agent autonomy♦ Scalability, fault-tolerance, reliability
P2PWNC as a P2P System
♦ Underused resources♦ Residential hotspots typically operate only at a small
percentage of maximum throughput
♦ Cost-sharing♦ Distribute cost among participating administrative
domains♦ High cost for a single provider to cover large areas
♦ Hardware ♦ Administration, operations, maintenance
♦ Decentralized control♦ Distributed accounting to track who owes who and
how much
♦ Agent autonomy♦ Can dynamically adjust provisioning rates
Architectural Overview
♦ Unique logical name for each DA♦ Can reuse DNS name
♦ Registered users♦ Local users of a particular domain♦ Examples:♦ Residential hotspot: all household
members♦WISP: all subscribers
♦ Roaming users♦ Visiting users from another domain
DA Modules
♦ Name service♦ Maps logical P2PWNC domain names to IP
addresses of DAs♦ Authentication
♦ Maintains a database of registered users along with security credentials
♦ Traffic-policing♦ Logs and shapes internet traffic♦ Allocates specific amounts of bandwidth to
visitors♦ WLAN
♦ Firewall, DHCP, DNS, access point control♦ Distributed accounting
♦ Secure storage of accounting data
DA Modules (2)
♦ Consumer-strategy♦ Home DA’s consumer-strategy is
contacted when roaming user wants service
♦ Decides if transaction should continue♦ Pays required tokens to visited DA’s
provider-strategy module♦ Provider-strategy♦ Decides whether to provide service to
visitor♦ Decides current service prices
DA Modules (3)
♦ Privacy-enhancement♦ Protects identity privacy♦Hides user name and home DA of
roaming user from visited DA
♦ Protects location privacy♦Hides visited DA from home DA
♦ Distributed Hash Table♦ Low-level module used by name
service and distributed accounting
Security and Privacy Issues
♦ Abuse by untrustworthy visitors♦ Illegal activities
♦ Traffic logging by untrustworthy providers♦ Possible solution: tunneling through
trusted gateway (e.g. home DA)
♦ Identity privacy♦ Possible solution: create a new alias for
every new connection?
♦ Identity and location privacy♦ Possible solution: Mix network
Mix network
Peer ‘P’(provider)
Peer ‘A’(mix 1)
Peer ‘B’(mix 2)
Peer ‘C’(home)
“My P2PWNC ID is Alias_X@A”
Credentials include real ID and a mix chain encrypted using nested public-key encryptions
Alias_X@A{ MIX, B, { MIX, C, { STOP, X }C }B }A
Alias_X@B{ MIX, C, { STOP, X }C }B
Alias_X@C{ STOP, X }C
X@CIdea credit: David Chaum
Slide credit: George Polyzos
Economic Considerations
♦ Optimal system parameters♦ Consumer/Provider strategies, token prices
♦ Secure distributed accounting subsystem♦ Monitors peer contribution and consumption♦ Uses cryptographically secure tokens (cannot be
forged)
♦ Domain strategies♦ How to charge usage:
♦ KBytes or hour, current congestions levels, identity of consumer
♦ How to balance conflicting requirements:♦ Want best possible service for its own roaming users♦ Must provide service to visitors to earn tokens for use
by roaming users♦ May affect service provided to its own local users
Economic Considerations (2)
♦ Offline DAs♦ Problem
♦ Roaming user requests service from visited DA♦ Visited DA unable to contact home DA
♦ Possible Solution (decentralized version)♦ Home DA distributes token allowances to users♦ User pays without intervention of home DA
♦ Token generation♦ How DAs first acquire tokens♦ Distributed banks generate tokens and
distribute to new entrants
Economic Considerations (3)
♦ Domain heterogeneity ♦ Different in terms of:
♦ Coverage size♦ Coverage location♦ Number of registered users
♦ Problem:♦ Domains with few visitors, difficult to earn tokens♦ Possible solution: set high token prices
♦ More general problem:♦ How to make sure a few domains don’t
monopolize all tokens?
Summary of DA Responsibilities
♦ Regulate prices for service♦ Make sure visitor traffic does not
adversely affect traffic from registered users
♦ Ensure best possible treatment for own (registered) users that are roaming
Business Models - Who can make a profit
♦ Upstream ISPs that allow P2PWNC may be preferred by customers
♦ “Pay-as-you-go” domains♦ Vendors can sell pre-paid cards
containing P2PWNC user id and credentials
♦ Virtual P2PWNC♦ Virtual DA obtains tokens from P2PWNC
domains outside normal interaction model♦ Sells tokens in the form of pre-paid cards
Business Models – Who can make a profit (2)
♦ P2PWNC domain aggregators♦ Host DA for multiple small WLANs♦ Similar to web hosting
♦ Vendors of DA modules♦ Provide consumer-strategy and
provider-strategy modules♦ Hotspot indexing engines♦ Tune DA parameters♦ Security and privacy enhancements
Operational Issues
♦ Need more economic analysis and simulations♦ How P2PWNC and token-based
incentive operate in real-world environment
♦ Regulatory obstacles♦ Some ISPs prohibit sharing of
broadband connections
P2PWNC Implementation
♦ http://mm.aueb.gr/research/p2pwnc
♦ GPL Licensed♦ AP: Linksys WRT54GS♦ Firmware
♦ Client: QTEK 9100♦ C and Java
Implementation Assumptions
♦ Good♦ No central authority♦ Users may use unlimited, free IDs♦ User consumption is not homogeneous♦ Software can be modified/hacked♦ Teams (domains) will try and cheat♦ Teams will collude
♦ Not so good♦ Team consumption is homogeneous♦ Team members trust each other♦ ISPs allow connection sharing
Receipt accounting
CO
NN
C
P
CA
CK R
CPT
RR
EQ
RC
PT
RR
EQ
RR
EQ
RC
PT
R
t0 w2
t0 w2
t0 w1?
provider, team timestamp, weight
Decentralized
♦ One receipt server per team♦ Gossiping protocol♦ Devices carry a sample of receipts♦ Consumers share receipts with
providers
♦ Adds overhead for verifying receipts
♦ Incomplete view of the “receipt graph”
Maxflow decision
♦ Probability of me granting you service
1,)(
)(min
PCmf
CPmfp
What IOU
What you owe me
Abuse
♦ Uncooperative teams♦ Evident from receipt graph♦ Other teams will stop providing
service
♦ DOS attacks♦ Centralized server is vulnerable♦ Decentralized servers have secret IPs♦ Teams do not communicate via Internet
♦ Colluding teams…
Generalized Maxflow
♦ Look for collusion hub X0
♦ Discount suspicious paths♦ Discount flow passing through
vertices with a high sum of outgoing edge weights
♦ Discount flow passing through many vertices
♦ Assumes homogeneous team usage
Security
♦ Team leader♦ Public/private keys for team identity♦ Signs member certificates
♦ Team members♦ Public/private keys for member identity
♦ All receipts are signed♦ Elliptic Curve Digital Signature Algorithm
(ECDSA)♦ Signing faster than verification♦ Mobile devices have limited computing
power
♦ No central authority (decentralized)
Simulation
♦ Providers and consumers make decisions based on benefit-to-cost ratio♦ Evolutionary learning♦ Providing +cost, consuming +benefit
♦ Simulate interaction across 500 rounds♦ 1 new team added per round♦ 300 total teams
Strategies
♦ Switch to best strategy after each round♦ Most teams adopt cooperative
strategies♦ After 500 rounds♦ 175 Reciprocative teams♦ 100 Unconditional cooperator teams♦ 20 Random cooperator teams♦ 5 Unconditional defector teams
Questions
♦ Will it work in the real world?♦ Sporadic usage♦ Receipt history flushing
♦ Is it scalable?♦ Maxflow could get expensive
♦ What about heterogeneous team usage?♦ Variable cost of bandwidth
♦ Who is responsible for the AP’s traffic?♦ Will the RIAA believe it wasn’t you?
P2PWNC Publications
♦ Initial idea♦ A Peer-to-Peer Approach to Wireless
LAN Roaming. Efstathiou EC, Polyzos GC. ACM WMASH, 2003.
♦ Implementation details♦ Stimulating Participation in Wireless
Community Networks. Efstathiou EC, Frangoudis PA, Polyzos GC. IEEE INFOCOM, 2006.
Real-World Example - FON
♦ Largest WiFi community in the world
♦ Idea♦ Members (aka Foneros) share wireless
Internet access at home♦ In return, get free WiFi wherever
there is a Fonero Access Point♦Use Fonero login
♦ How to become a member:♦ Buy a WiFi router (aka La Fonera)
from FON
More about FON
♦ 3 types of Foneros (members)♦ Linuses
♦ People who share home WiFi to get free WiFi wherever there is a FON Access Point
♦ Aliens♦ People who do not share their WiFi but want access
to a FON Access Point♦ Charged $3 per day
♦ Bills♦ Businesses who want to make money off their WiFi♦ Don’t want free roaming♦ Get 50% of money Aliens pay♦ Can advertise on their own personalized FON
Access Point homepage